ICRISAT Designs Improved Cropping Systems for Sahelian Millet, Cowpeas
Gradually, Africa is becoming the world's leading producer of millet. In the quarter century since the early 1970s, African millet harvests increased 22 percent, whereas other regions registered substantial production declines. The percentage of millet used for domestic food consumption is rising steadily in Africa, but the vast and still expanding millet areas continue to produce low, but steady, yields with very few fertilizer inputs. Soon, Africa is likely to have the largest millet acreage of all developing regions with yields only slightly below the developing country average. With 20 kilograms a year, Africans eat four times as much millet per capita as the second largest consumers, Asians.
The harsh environment of the Sahelian region presents special problems to increasing millet yields. While crop improvement research can partially help increase drought and heat tolerance, over four-fifths of the potential yield gains from overcoming these drawbacks must come from improved natural resource management, says the International Crops Research Institute for the Semi-Arid Tropics.
Traditional cropping systems in the Sahel are essentially a continuous millet/cowpea intercrop grown at low plant populations with no chemical fertilizers and all production operations done manually.
ICRISAT agronomists, working with scientists from national agricultural research programs, have developed improved systems that offer Sahelian farmers better alternatives to growing continuous millet/cowpea intercrops. The new systems were designed in response to specific constraints in the traditional systems -- low plantings, losses in productivity caused by soil nutrient deficits as fallow periods are shortened because of population pressure, poor soils, and a shortage of farm labor.
Experiments conducted at the ICRISAT Sahelian Center and on farms in Niger betweeen 1986 and 1993 compared fertility, productivity, and labor demand in the new systems with those of traditional practices. The millet/cowpea intercrop was compared with only millet, only cowpea, and millet/cowpea rotations.
The new systems received a phosphate fertilizer, and were sown at higher than traditional densities. The phosphorus application clearly improved yields of both cowpea and millet. Rotating a millet-cowpea intercrop with only cowpeas boosted both productivity and fertility, but required more labor than the continuous millet/cowpera intercrop. Estimates of productive capacity showed that in most years, the new systems use resources more efficiently than the traditional system. The highest yields were obtained when sole millet was rotated with sole cowpea.
Follow-up studies will determine the sustainability of the new cropping systems.
Pheromones Effective in Controlling Millet Stem Borers
Meanwhile, ICRISAT scientists have found that pheromone technology has proved to be highly effective in monitoring the millet stem borer, a major pest in sub-Saharan Africa that causes crop losses estimated at $91 million a year.
Pheromones can be used to reduce millet stem borer populations. ICRISAT entomologists were able to reduce borer matings to a tenth of normal levels by dispersing pheromones over a field in traps, thus disrupting mating. Borers find potential mates by tracking the odor of pheromones to their source.
Mass trapping using pheromones was tried in farmers' fields in Niger last year. These traps, scientists said, were particularly effective along fences and granaries, areas that harbor borers. Results indicate that inexpensive, locally-made pheromone-baited traps are efficient and well-adapted to local conditions.